The present invention relates to semiochemical delivery systems useful for attracting a target insect to a selected location and to disrupt normal insect mating behavior. The invention provides a negatively charged chitosan derivative, e.g., NOCC-based, semiochemical delivery system which releases a semiochemical material into the atmosphere at a sustained rate over an extended period of time.
Semiochemicals are the broad category of naturally occurring compounds that produce odors which play a key role in the lives of insects, assisting them to locate food, water, and mating partners, and also serve as warning signals of impending danger. For example, certain semiochemicals such as sex-pheromones are species-specific communication chemicals which attract mating partners. Sex pheromones are emitted by either male or female insects. Other semiochemicals such as allomones are inter-species compounds that are primarily beneficial to the species releasing the odor. For example, allomones released from flower blossoms attract pollinators, and such pollination benefits the flower while the pollen provides a food source to the pollinator.
The ability of semiochemicals to influence insect behavior is also interrelated with environmental conditions such as temperature, humidity, barometric pressure, wind movement, and exposure to sunlight. In addition, the ability of semiochemicals to influence insect behavior is dependent upon biological factors associated with the insect population such as insect age, and gender ratio and distribution.
Controlled release of semiochemicals to influence insect behavior is a potentially valuable tool for agricultural management. For example, controlled release of semiochemicals at a sustained rate over an extended period of time may potentially be used to monitor an insect population by capturing insects over an entire growing season. In addition, such controlled release of semiochemicals may potentially be used as a biopesticide to disrupt mating patterns of insects harmful to a specific agricultural or forestry product.
Researchers have evaluated several types of semiochemical delivery systems for the controlled release of semiochemicals, but problems related to short field life, application difficulty and inconsistent release rates under field conditions have decreased efficiency. Dispensers evaluated for semiochemical delivery include rubber tubing, see Mani et al., "Bekampfung des Apfelwicklers (Cydia pomonella L.) mit der Verwirrungsmethode in Einer Obstanlage im Bundner Rheintal", 1979-81 Mitt. Schweiz. Entomol. Ges. 57, pp. 341-348 (1984); microcapsules, see Charmillot & Bloesch, "La Technique de Confusion Sexuelle: un Moyen Specifique de Lutte Contre le Carpocapse Cydia pomonella", L. Rev. Suisse Vitic. Arboric. Hortic. 19, pp. 129-138 (1987); laminated plastic flakes, see Charmillot & Bloesch, id; Audemard, "Confusion Sexuelle avec des Pheromones en Europe De L'Ouest", Agric. Ecosyst. Environ. 21, pp. 101-110 (1988); hollow fiber tapes, see Reissig et al., "Insect Management in Disease-Resistant Dwarf and Semi-Dwarf Apple Trees", Environ. Entomol. 13, pp. 1201-1207 (1984); chopped hollow fibers, see Moffitt & Westigard, "Suppression of the Codling Moth (Lepidoptera; Tortricidae) Population on Pears in Southern Oregon Through Mating Disruption with Sex Pheromone", J. Econ. Entomol. 77, pp. 1513-1519 (1984); and polyethylene stripes, see Brown et al., "Insect Sex Pheromones: Formulations to Increase the Stability of Conjugated Dienes", J. Econ. Entomol. 79, pp. 922-927 (1986).
Researchers have also experimented with different combinations of semiochemicals to increase the efficiency of semiochemical delivery systems for the controlled release of semiochemicals. For example, researchers identified that spheres baited with a combination of semiochemicals relating to mating and feeding attracted more insects compared with spheres baited with either a mating or a feeding semiochemical alone. However, semiochemical delivery systems have the tendency to break down under conditions of high humidity. See J. J. Duan et al., Advancements in Second-stage Apple IPM: Combination of Fruit and Food Odor to Increase Captures of apple Maggot Flies on Sticky Red Spheres, Fruit Notes 4, 6 (Fall, 1991).
Negatively charged chitosan derivative materials may be excellent candidates for the controlled release of semiochemicals because of their unique properties. In particular, a novel derivative of carboxymethylchitosan, N,O-carboxymethylchitosan ("NOCC") disclosed by Hayes in U.S. Pat. No. 4,619,995 (the disclosure which is incorporated herein by reference), which has carboxymethyl substitutes on some of both the amino and primary hydroxyl site of the glucosamine units of the chitosan structure may be used in an uncrossed linked form as a solution, or may be covalently crosslinked or non-covalently complexed into a gel. Thus, it may be possible that the various forms of NOCC allow application of the material in different forms to provide semiochemical delivery systems tailored to specific applications. In addition, semiochemicals that possess aldehyde or amino groups may be bonded directly to the NOCC polymer and the release rate controlled by the slow breakdown of the imine bond. Further, a surfactant or oil may be added as an agent which assists in the maintenance of semiochemicals in the gel, or substitutents with surfactant function can be chemically bonded to the polymer chain. Either approach alters the rate of release of the semiochemical. Since NOCC polymers are biodegradable to simple sugars, there is no polluting residue after the NOCC polymers have released the semiochemicals. Finally, chitin, which may be chemically modified to form NOCC polymers, can be cheaply obtained from the shells of crustaceans and many insects, waste products that would otherwise have to be disposed. Thus, negatively charged chitosan derivative materials, and NOCC in particular, present advantageous properties for use in insect management, because of their unique properties and low cost.
Accordingly, an object of the present invention is to provide a method of using a negatively charged chitosan derivative, e.g., NOCC-based, semiochemical delivery system to attract a target insect to a selected location.
Another object of the invention is to provide a method of using a negatively charged chitosan derivative, e.g., NOCC-based, semiochemical delivery system to monitor a target insect population by attracting the target insect to a selected location.
A further object of the invention is to provide a method of using a negatively charged chitosan derivative semiochemical, e.g., NOCC-based, delivery system to disrupt the mating patterns of a target insect by providing a sufficient level of the semiochemical over a diffuse area.
A still further object of the invention is to provide a method of using a negatively charged chitosan derivative semiochemical, e.g., NOCC-based, delivery system to release a volatile semiochemical at a sustained rate over an extended period of time to attract a target insect to a selected location or to disrupt mating behavior.
A still further object of the invention is to provide a negatively charged chitosan derivative, e.g., NOCC-based, semiochemical delivery system which releases a volatile semiochemical at a sustained rate over an extended period of time to attract a target insect to a selected location or to disrupt mating behavior.
These and other objects and features of the invention will be apparent from the following description and the drawing.